Systems and methods for soda ash production

ABSTRACT

Provided herein are methods and systems to produce sodium carbonate (soda ash). The methods and systems provided herein modify a Solvay process by integrating it with an electrochemical process to produce a less carbon dioxide intensive Solvay process and an environmentally friendly sodium carbonate product.

CROSS-REFERENCE

This application claims priority to U.S. Provisional Application No.61/431,767, filed Jan. 11, 2011 and U.S. Provisional Application No.61/446,482, filed Feb. 24, 2011, both of which are incorporated hereinby reference in their entireties. This application is related to thefollowing patent applications: U.S. Provisional Patent Application No.61/081,299, filed 16 Jul. 2008, titled “Low Energy pH Modulation forCarbon Sequestration Using Hydrogen Absorptive Metal Catalysts”; U.S.Provisional Patent Application No. 61/091,729, filed 25 Aug. 2008,titled “Low Energy Absorption of Hydrogen Ion from an ElectrolyteSolution into a Solid Material”; U.S. Provisional Patent Application No.61/222,456, filed 1 Jul. 2009, titled “CO₂ Utilization InElectrochemical Systems”; and PCT Patent Application No. PCT/US09/48511,filed on 25 Jun. 2009, titled “Low Energy 4-Cell Electrochemical Systemwith Carbon Dioxide Gas,” each of which is incorporated herein byreferences in its entirety.

BACKGROUND

The Solvay process, also referred to as the ammonia-soda process, is anindustrial process for production of soda ash (sodium carbonate). Theingredients for this process may be readily available: salt brine (frominland sources or from the sea) and limestone (from mines). Carbondioxide is emitted from the use of soda ash, and is emitted duringproduction of soda ash, depending on the industrial process used tomanufacture soda ash. There is a need for systems and methods forproduction of soda ash in a less carbon dioxide-intensive manner.

SUMMARY

Provided herein is a novel and non-obvious process, machine,manufacture, and composition thereof.

In one aspect, there is provided a method to produce sodium carbonate,comprising: a) absorbing carbon dioxide in an ammonia solution to formsodium bicarbonate; and b) subjecting the sodium bicarbonate to a firstelectrochemical process to produce sodium carbonate. In one aspect,there is provided a method to modify a Solvay process to produce a lesscarbon dioxide intensive Solvay process, comprising: a) absorbing carbondioxide in an ammonia solution to form sodium bicarbonate; and b)subjecting the sodium bicarbonate to a first electrochemical process toproduce sodium carbonate, thereby resulting in a less carbon dioxideintensive Solvay process. In some embodiments of these aspects, themethod further comprises regenerating the ammonia solution using calciumoxide obtained by lime calcination. In some embodiments of theseaspects, the method further comprises regenerating the ammonia solutionusing sodium hydroxide obtained from the first or a secondelectrochemical process. In some embodiments of these aspects, themethod does not comprise bicarbonate calcination, lime calcination, or acombination thereof. In some embodiments of these aspects, the methodproduces less than 80% carbon dioxide as compared to a conventionalSolvay process. In some embodiments of these aspects, the method furthercomprises treating the sodium carbonate with calcium or magnesium ionsto form calcium carbonate, magnesium carbonate, or combination thereof.In some embodiments, the calcium carbonate, magnesium carbonate, orcombination thereof is a cementitious material. In some embodiments, thecementitious material comprises vaterite. In some embodiments, thecementitious material has a compressive strength of greater than 10 MPa.

In one aspect, there is provided a system comprising a Solvay systemintegrated with an electrochemical system, comprising: a) a Solvaysystem comprising an absorber configured to absorb carbon dioxide in anammonia solution to form sodium bicarbonate; and b) a firstelectrochemical system operably connected to the Solvay systemconfigured to convert the sodium bicarbonate to sodium carbonate. Insome embodiments of the systems, the system further comprises aregenerator operably connected to the Solvay system configured toregenerate the ammonia solution after absorption of the carbon dioxidein the ammonia solution. In some embodiments of the systems, the systemfurther comprises a lime calciner operably connected to the regeneratorand configured to produce calcium oxide for regenerating the ammoniasolution. In some embodiments of the systems, the system furthercomprises a second electrochemical system operably connected to theregenerator and configured to produce sodium hydroxide for regeneratingthe ammonia solution. In some embodiments of the systems, the systemfurther comprises a precipitator operably connected to the firstelectrochemical system configured to produce calcium and/or magnesiumcarbonate by treating sodium carbonate with calcium and/or magnesiumions.

DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 provides the Solvay process for preparing soda ash.

FIG. 2 is an illustrative embodiment of a modification of the Solvayprocess incorporating electrochemical process.

FIG. 3 is an illustrative embodiment of another modification of theSolvay process incorporating electrochemical process.

FIG. 4 is an illustrative embodiment of yet another modification of theSolvay process incorporating two electrochemical processes.

FIG. 5 is an illustrative embodiment of a process for producing soda ashfrom direct capture of carbon dioxide.

FIG. 6 is an illustrative embodiment of a comparison of carbon dioxideemissions from the processes illustrated in FIGS. 1-5.

FIG. 7 is an illustrative embodiment of a process for producing soda ashfrom alkaline brines in accordance with the existing process by SearlesValley Minerals (Overland Park, Kans.).

FIG. 8 is an illustrative embodiment of a modification of the SearlesValley Minerals process incorporating electrochemical process.

FIG. 9 is an illustrative embodiment of a process for producing soda ashfrom alkaline brines incorporating electrochemical process.

FIG. 10 is an illustrative embodiment of a comparison of carbon dioxideemissions from the processes provided in FIGS. 7-9 and a direct captureof carbon dioxide.

FIG. 11 is an illustrative embodiment of a typical process forconverting trona to soda ash.

FIG. 12 is an illustrative embodiment of a process for producing sodaash from trona utilizing electrochemical process.

FIG. 13 provides an illustrative embodiment of an electrochemicalsystem.

FIG. 14 provides an illustrative embodiment of an electrochemicalsystem.

FIG. 15 provides an illustrative embodiment of an electrochemicalsystem.

FIG. 16 provides an illustrative embodiment of an electrochemicalsystem.

FIG. 17 provides an illustrative embodiment of a Solvay systemintegrated with the electrochemical system.

FIG. 18 provides an illustrative embodiment of a processing system.

FIG. 19 illustrates a plot comparing the performance between 10 wt %NaOH and 1 mol/L sodium bicarbonate solution in an electrochemical cell.

DESCRIPTION

Described herein are methods and systems to produce sodium carbonate byintegrating Solvay process with electrochemical processes. The methodsand systems provided herein are devoid of calcination of bicarbonate andlime as found in a conventional Solvay process, thereby providing a lesscarbon dioxide intensive Solvay process and an environmentally friendlysodium carbonate product.

It is to be understood that the invention is not limited to particularembodiments described herein as such embodiments may vary. It is also tobe understood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting, since the scope of the invention will be limited only by theappended claims. Unless defined otherwise, all technical and scientificterms used herein have the same meaning as commonly understood by one ofordinary skill in the art to which this invention belongs.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range, is encompassed. The upper and lower limits of thesesmaller ranges may independently be included in the smaller ranges andare also encompassed, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

Certain ranges are presented herein with numerical values being precededby the term “about.” The term “about” is used herein to provide literalsupport for the exact number that it precedes, as well as a number thatis near to or approximately the number that the term precedes. Indetermining whether a number is near to or approximately a specificallyrecited number, the near or approximating unrecited number may be anumber, which, in the context in which it is presented, provides thesubstantial equivalent of the specifically recited number.

All publications, patents, and patent applications cited in thisspecification are incorporated herein by reference to the same extent asif each individual publication, patent, or patent application werespecifically and individually indicated to be incorporated by reference.Furthermore, each cited publication, patent, or patent application isincorporated herein by reference to disclose and describe the subjectmatter in connection with which the publications are cited. The citationof any publication is for its disclosure prior to the filing date andshould not be construed as an admission that the claimed invention isnot entitled to antedate such publication by virtue of prior invention.Further, the dates of publication provided may be different from theactual publication dates, which may need to be independently confirmed.

It is noted that, as used herein and in the appended claims, thesingular forms “a,” “an,” and “the” include plural references unless thecontext clearly dictates otherwise. It is further noted that the claimsmay be drafted to exclude any optional element. As such, this statementis intended to serve as antecedent basis for use of such exclusiveterminology as “solely,” “only” and the like in connection with therecitation of claim elements, or use of a “negative” limitation.

As will be apparent to those of skill in the art upon reading thisdisclosure, each of the individual embodiments described and illustratedherein has discrete components and features which may be readilyseparated from or combined with the features of any of the other severalembodiments. Any recited method can be carried out in the order ofevents recited or in any other order, which is logically possible.Although any methods and materials similar or equivalent to thosedescribed herein may also be used in the practice or testing of theinvention, representative illustrative methods and materials are nowdescribed.

Methods and Systems

A “Solvay process,” as used herein, includes any process that can beused to produce sodium carbonate using ammonia and carbon dioxide. About25 percent of the world production of soda ash may be from naturalsodium carbonate bearing deposits referred to as natural processes. Forexample, during the natural production process, trona (a principal orefrom which natural soda ash may be made) may be calcined in a rotarykiln and chemically transformed into a crude soda ash. However, carbondioxide is generated in the process. In the Solvay process, asillustrated in FIG. 1, sodium chloride brine, limestone, coke andammonia are the raw materials in a series of reactions leading to theproduction of soda ash. Ammonia may be regenerated while a small amountmay be lost. From the series of reactions illustrated in FIG. 1, CO₂ isgenerated in two calcination processes. The CO₂ generated may becaptured, compressed and directed to Solvay precipitating towers forconsumption in a mixture of brine (aqueous NaCl) and ammonia. However,there is net CO₂ emitted to the atmosphere during the production of sodaash because more CO₂ is produced by calcining limestone than isstoichiometrically required for absorption. The methods and systemsdescribed herein are related to the reduction of the CO₂ emission fromthe Solvay process by eliminating one or both of the calcining steps.The calcining steps of the Solvay process may be replaced by theelectrochemical processes described herein.

The Solvay process (as illustrated in FIG. 1) benefits frommodifications comprising one or more elements of the processing and/orelectrochemical systems and methods described herein. In someembodiments, for example, some of the carbon dioxide emitted from theSolvay process may be processed in accordance with any of theCO₂-processing methods described herein. In such embodiments, the carbondioxide may originate from Reaction IV (“Bicarb Calcination”), ReactionII (“Lime Calcination”), or a combination thereof. In addition, calciumchloride, which is produced in Reaction III (“Regeneration”) in FIG. 1,may be used in some embodiments to produce calcium and/or magnesiumcarbonates (e.g., calcite, aragonite, vaterite, amorphous calciumcarbonate) in the processes described herein. Such calcium and/ormagnesium carbonates are useful in building materials such as cement,aggregate, supplementary cementitious materials, and the like. Alkalinewaste and/or by-products of the Solvay process may also be used in theCO₂-process described herein.

In one aspect, there is provided a method to produce sodium carbonate,comprising a) absorbing carbon dioxide in an ammonia solution to formsodium bicarbonate; and b) subjecting the sodium bicarbonate to a firstelectrochemical process to produce sodium carbonate. In one aspect,there is provided a method to produce sodium carbonate, comprising a)absorbing carbon dioxide in an ammonia solution to form sodiumbicarbonate; b) subjecting the sodium bicarbonate to a firstelectrochemical process to produce sodium carbonate; and c) regeneratingthe ammonia solution using calcium oxide obtained by lime calcinations.In one aspect, there is provided a method to produce sodium carbonate,comprising a) absorbing carbon dioxide in an ammonia solution to formsodium bicarbonate; b) subjecting the sodium bicarbonate to a firstelectrochemical process to produce sodium carbonate; and c) regeneratingthe ammonia solution using sodium hydroxide obtained from the first or asecond electrochemical process. The first and/or the secondelectrochemical processes may be any electrochemical process describedherein.

In another aspect, there is provided a method to modify a Solvay processto produce a less carbon dioxide intensive Solvay process, comprising a)absorbing carbon dioxide in an ammonia solution to form sodiumbicarbonate; and b) subjecting the sodium bicarbonate to a firstelectrochemical process to produce sodium carbonate, thereby resultingin a less carbon dioxide intensive Solvay process. In one aspect, thereis provided a method to modify a Solvay process to produce a less carbondioxide intensive Solvay process, comprising a) absorbing carbon dioxidein an ammonia solution to form sodium bicarbonate; b) subjecting thesodium bicarbonate to a first electrochemical process to produce sodiumcarbonate; and c) regenerating the ammonia solution using calcium oxideobtained by lime calcinations, thereby resulting in a less carbondioxide intensive Solvay process. In one aspect, there is provided amethod to modify a Solvay process to produce a less carbon dioxideintensive Solvay process, comprising a) absorbing carbon dioxide in anammonia solution to form sodium bicarbonate; b) subjecting the sodiumbicarbonate to a first electrochemical process to produce sodiumcarbonate; and c) regenerating the ammonia solution using sodiumhydroxide obtained from the first or a second electrochemical process,thereby resulting in a less carbon dioxide intensive Solvay process. Thefirst and/or the second electrochemical processes may be anyelectrochemical process described herein. In some embodiments, themethod described above and herein produces less than 80% carbon dioxideas compared to a conventional Solvay process. In some embodiments, themethod described above and herein produces less than 90%; or less than80%; or less than 70%; or less than 60%; or less than 50%; or less than40%; or less than 30%; or less than 20%; or less than 10%; or less than5%; or less than 5-90%; or less than 5-80%; or less than 5-70%; or lessthan 5-60%; or less than 5-50%; or less than 5-40%; or less than 5-30%;or less than 5-20%; or less than 5-10%; or less than 10-80%; or lessthan 25-80%; or less than 50-80%; as compared to a conventional Solvayprocess.

For the methods described herein and as above, the methods do notinclude bicarbonate calcination, lime calcination, or a combinationthereof.

FIGS. 2-5 provide some modifications to the Solvay process of FIG. 1.FIG. 2, for example, illustrates an electrochemical process in place ofReaction IV (“Bicarb Calcination”). The electrochemical process is asdescribed herein. Details of such a modification, as provided in FIG. 2,show that Reaction IV of the modified process does not produce carbondioxide, a distinct advantage over the existing Solvay process. FIG. 3,for example, illustrates an electrochemical process in place of ReactionII (“Lime Calcination”). The electrochemical process is as describedherein. Details of such a modification, as provided in FIG. 3, show thatReaction II of the modified process does not produce carbon dioxide, adistinct advantage over the existing Solvay process. FIG. 4, forexample, illustrates two electrochemical processes, one for Reaction IV(“Bicarb Calcination”) and the other for Reaction II (“LimeCalcination”). Details of such a modification as provided in FIG. 4,illustrate that Reactions II and IV of the modified process do notproduce carbon dioxide, a distinct advantage over the existing Solvayprocess. FIG. 5, for example, illustrates a direct capture feature ofFIG. 4 as well as a modified Reaction III (“Regeneration”). Some of theadvantages of the modified Solvay process are lower demand for rawmaterials in Reactions I and III; less carbon dioxide emissions; andless energy intensive reactions (reduced or no calcinations). FIG. 5shares the same soda ash product as the Solvay process but excisesReactions II and III and completely modifies Reactions I and II.Additional advantages of the processes provided in FIGS. 2-5 areprovided in the Table I immediately below.

TABLE I Replace Bicarb Replace Lime Calcination Calcination Replace BothCO₂ 50% of total CO₂ 100% of total CO₂ 100% of total CO₂ Capture Use of50% reduction 100% reduction 100% reduction CaCO₃ Capex 1) Bicarb 1)Lime 1) Lime and bicarb calcination calcination calcination eliminatedeliminated eliminated 2) NH₃ absorption 2) NH₃ absorption and limecalcination reduced by 50% reduced by 50%

In addition to the advantages provided in the Table I, the processes ofFIGS. 2-5 are less energy intensive and have smaller carbon footprintthan the conventional Solvay process of FIG. 1. For example, FIG. 6illustrates carbon dioxide emissions in tonnes CO₂/tonne of soda ashproduced for the processes depicted in FIGS. 1-5, which correspond to“Solvay w/ Electrochemical process”, “Solvay w/ NaOH Regeneration”,“Solvay w/ two Electrochemical processes”, and “Direct Capture”.Advantageously, “Solvay w/ Electrochemical process”, “Solvay w/ NaOHRegeneration”, “Solvay w/ two Electrochemical processes”, and “DirectCapture,” (respectively FIGS. 2-5) each emit less carbon dioxide (ameasure of energy efficiency) than the Solvay process provided inFIG. 1. In one aspect, there is provided a method to produce sodiumcarbonate, comprising a) absorbing carbon dioxide in sodium carbonatesolution to form sodium bicarbonate; and b) subjecting the sodiumbicarbonate to an electrochemical process to produce sodium carbonate.In another aspect, there is provided a less carbon dioxide intensivemethod to produce sodium carbonate, comprising a) absorbing carbondioxide in sodium carbonate solution to form sodium bicarbonate; and b)subjecting the sodium bicarbonate to an electrochemical process toproduce sodium carbonate, thereby resulting in a less carbon dioxideintensive method to produce sodium carbonate. FIG. 7 illustrates aprocess using Searles Valley Minerals (SVM) for producing soda ash. Amodification to the process is illustrated in FIG. 8. In accordance withpreviously described process modifications, the process of FIG. 8replaces the bicarbonate calcination step with an electrochemical step,which electrochemical step does not release carbon dioxide. FIG. 9provides a process for producing soda ash in which there is anelectrochemical step replacing the bicarbonate calcination step alongwith recycling of acid. Additional details for the processes of FIGS.8-9 are provided in each figure. Some of the advantages of the processesprovided in FIGS. 8-9 are provided in the Table II below.

TABLE II SVM Brines w/ ABLE C SVM Brines w/ Acid Recycle Captured CO₂100% of total CO₂ N/A Brine usage Reduces brine usage by N/A 50% Sodiumsulfate Available on site Available on site (can be recycled and/orsold) Sulfuric acid Used on site (for borate Used on site processing)(for brine titration) Capex 1) Bicarb calcination 1) Bicarb calcinationeliminated eliminated 2) MEA absorber and regeneration systemseliminated

In addition to the advantages provided in Table II, the processes ofFIGS. 8-9 are less energy intensive and have smaller carbon footprintsthan the Searles Valley Minerals process of FIG. 7. For example, FIG. 10illustrates carbon dioxide emissions in tonnes CO₂/tonne of soda ashproduced for the processes depicted in FIGS. 8-9, which correspond to“Alkaline Brines w/ Electrochemical process,” “Alkaline Brines w/ AcidRecycle,” and “Direct Capture,” respectively, in FIG. 10.Advantageously, “Alkaline Brines w/ Electrochemical process,” “AlkalineBrines w/ Acid Recycle,” and “Direct Capture,” each emit less carbondioxide (a measure of energy efficiency) than the Searles ValleyMinerals process provided in FIG. 7. The direct capture is same as thedirect capture provided in FIG. 5.

FIG. 11 illustrates a conventional trona ore process where trona iscalcined to form soda ash. FIG. 12 illustrates modification to thetrona-based method for producing soda ash, modifications including, butnot limited to, use of electrochemistry and/or CO₂ processing (e.g.,processing waste CO₂ produced by calcination of trona). FIG. 12illustrates one such method for producing soda ash in a less carbondioxide intensive manner. As illustrated, soda ash may be prepared fromtrona (½Na₂CO₃.NaHCO₃.2H₂O (s)) utilizing electrochemistry in place of,or in combination with, calcination. As such, in some embodiments, tronamay be mined and/or ground, for example, to a powder that may be useddirectly in electrolyte (e.g. catholyte) for the electrochemical cell orsystem thereof (e.g. stack of electrochemical cells), or purified beforeelectrolyte use to remove impurities. While any of a number ofadditional salts may be used in electrolyte for the electrochemicalcell(s) or system(s) thereof as described herein, FIG. 12 illustratesuse of either Na₂SO₄ or NaCl, which provide anolytes comprising H₂SO₄ orHCl, respectively. Carbonates, as shown in FIG. 12 and described herein,may be electrochemically produced at a low voltage across the anode andthe cathode (e.g., 1.2 V), which lowers the carbon dioxide footprint ofthe process provided in FIG. 12 when compared to the basic processprovided in FIG. 11. Following production, such carbonates (e.g.,Na₂CO₃) may be further processed including, but not limited to,liquid-solid separation, crystallization, recrystallization, and drying.As such, the system component corresponding to the mining/grinding stepmay comprise a mineral processor configured to comminute trona and otherrocks/minerals; the system component corresponding to theelectrochemical step may comprise an electrochemical cell or stack ofelectrochemical cells; and the system components corresponding tocrystallization and drying may comprise a liquid-solid separator, a tankor analogous vessel for crystallization/recrystallization, and/or adryer (e.g., spray dryer).

Advantageously, “Trona Ore w/ Electrochemical process” emits less carbondioxide (a measure of energy efficiency) than the Trona Ore processprovided in FIG. 11. In addition to the process of FIG. 12 being lessenergy intensive and having smaller carbon footprints than the Trona Oreprocess of FIG. 11, the process of FIG. 12 has additional advantagesincluding, but not limited to, eliminating CO₂ emissions fromcalcination.

In one aspect, there is provide a system comprising a Solvay systemintegrated with an electrochemical system, comprising a) a Solvay systemincluding an absorber configured to absorb carbon dioxide in an ammoniasolution to form sodium bicarbonate; and b) a first electrochemicalsystem operably connected to the Solvay system configured to convert thesodium bicarbonate to sodium carbonate. In another aspect, there isprovide a system comprising a Solvay system integrated with anelectrochemical system, comprising a) a Solvay system including anabsorber configured to absorb carbon dioxide in an ammonia solution toform sodium bicarbonate; b) a first electrochemical system operablyconnected to the Solvay system configured to convert the sodiumbicarbonate to sodium carbonate; and c) a regenerator operably connectedto the Solvay system configured to regenerate the ammonia solution afterabsorption of the carbon dioxide in the ammonia solution. In yet anotheraspect, there is provide a system comprising a Solvay system integratedwith an electrochemical system, comprising a) a Solvay system includingan absorber configured to absorb carbon dioxide in an ammonia solutionto form sodium bicarbonate; b) a first electrochemical system operablyconnected to the Solvay system configured to convert the sodiumbicarbonate to sodium carbonate; c) a regenerator operably connected tothe Solvay system configured to regenerate the ammonia solution afterabsorption of the carbon dioxide in the ammonia solution; and d) a limecalciner operably connected to the regenerator and configured to producecalcium oxide for regenerating the ammonia solution. In yet anotheraspect, there is provide a system comprising a Solvay system integratedwith an electrochemical system, comprising a) a Solvay system includingan absorber configured to absorb carbon dioxide in an ammonia solutionto form sodium bicarbonate; b) a first electrochemical system operablyconnected to the Solvay system configured to convert the sodiumbicarbonate to sodium carbonate; c) a regenerator operably connected tothe Solvay system configured to regenerate the ammonia solution afterabsorption of the carbon dioxide in the ammonia solution; and d) asecond electrochemical system operably connected to the regenerator andconfigured to produce sodium hydroxide for regenerating the ammoniasolution.

The Solvay system is any system known in the art to carry out the Solvayprocess. The absorber in the Solvay system may be any absorberconfigured to absorb carbon dioxide in an ammonia solution, such as, butnot limited to, absorber configured for bubbling the carbon dioxide gas,stirrers for mixing the gas in the solution, packed bed for efficientcontact between the gas and the solution, etc. In some embodiments, thesolution charged with CO₂ is made by parging or diffusing the CO₂gaseous stream through an ammonia solution to make a CO₂ chargedsolution containing sodium bicarbonate. In some embodiments, the CO₂ gasis bubbled or parged through a solution containing ammonia in theabsorber. In some embodiments, the absorber may include a bubble chamberwhere the CO₂ gas is bubbled through the ammonia solution. In someembodiments, the absorber may include a spray tower where the ammoniasolution is sprayed or circulated through the CO₂ gas. In someembodiments, the absorber may include a pack bed to increase the surfacearea of contact between the CO₂ gas and the ammonia solution. In someembodiments, a typical absorber fluid temperature is 32-37° C. For someembodiments, the absorber for absorbing CO₂ in the solution may be asdescribed in U.S. application Ser. No. 12/721,549, filed on Mar. 10,2010, which is incorporated herein by reference in its entirety.

The regenerator in the system described herein may be any system thatcan be used for regenerating ammonia (from ammonium chloride) where thesystem contains the base (such as calcium oxide from lime calcinationsor sodium hydroxide from electrochemical process). For example,regenerator can be a tank, or a series of tanks, or container which maycontain conduits or pipes to transfer and mix the ammonium salt solutionand the base to regenerate ammonia. The ammonia formed may betransferred out of the tank or container using conduits or pipes.

The lime calciner in the system described herein may be any system thatcan be used for lime calcinations. Such calciners are well known in theart and are well within the scope of the invention.

In some embodiments, the sodium bicarbonate solution from the Solvayplant is transferred to the electrochemical system for the generation ofsoda ash. In some embodiments, the sodium hydroxide from theelectrochemical systems is transferred to the Solvay plant for theregeneration of the ammonia solution. In some embodiments, there areprovided methods and systems where the electrochemical systems of theinvention are set up on-site of the Solvay process where sodiumbicarbonate from the Solvay process is administered to theelectrochemical system to generate soda ash and the sodium hydroxidefrom the electrochemical process is used to regenerate ammonia solution.In some embodiments, the electrochemical plant may be fitted close tothe Solvay plant eliminating transportation cost for waste products andallowing transportation of valuable products only.

The electrochemical systems are as described herein below.

Electrochemical Processes and Systems

The “electrochemical process” or “electrochemical system” used in themethods and systems described above and herein are described in thissection. Accordingly, the methods and systems include one or morefeatures of the electrochemical process and electrochemical celldescribed herein below. For example, the electrochemical processdescribed in FIGS. 3 and/or 4 is any electrochemical process describedherein that produces sodium hydroxide in the catholyte. Similarly, theelectrochemical process described in FIGS. 2, 4, 5, 8, 9, and/or 12 isany electrochemical process described herein that contacts sodiumbicarbonate solution with the catholyte.

Described herein are electrochemical systems and methods where theelectrochemical cell electrolyzes a salt solution, such as, but notlimited to, sodium chloride solution to produce sodium hydroxide in thecatholyte and/or sodium carbonate ions and/or sodium bicarbonate in thecatholyte, and an acid in the anolyte. The systems and methods are notlimited to the use of sodium chloride solution as disclosed in theembodiments described herein as other salt solutions (e.g., aqueouspotassium sulfate, Na₂SO₄ (aq), etc.) can be used to produce anequivalent result. In preparing the electrolytes for the system, waterfrom various sources can be used including seawater, brackish water,brines or naturally occurring fresh water. In some embodiments, watermay be purified to an acceptable level for use in the electrochemicalsystem.

The electrochemical cell comprises an anode in contact with an anolyte;a cathode in contact with a catholyte; and an ion exchange membranedisposed between the catholyte and the anolyte. Accordingly, in oneaspect, there is provided a system comprising a Solvay system integratedwith an electrochemical system, comprising a) a Solvay system comprisingan absorber configured to absorb carbon dioxide in an ammonia solutionto form sodium bicarbonate; and b) a first electrochemical systemoperably connected to the Solvay system configured to convert the sodiumbicarbonate to sodium carbonate wherein the electrochemical systemcomprises an anode in contact with an anolyte, a cathode in contact witha catholyte and one or more of ion exchange membrane.

In some embodiments of the electrochemical systems, with reference toFIG. 13 herein, in some embodiments the alkaline solution is produced inthe catholyte of an electrochemical system 100 by electrolyzing a saltsolution e.g., sodium chloride solution to produce the alkalinesolution, e.g., sodium hydroxide in the catholyte, and an acid, e.g.,hydrochloric acid in the anolyte. The anode and the cathode may beseparated by an ion exchange membrane (IEM). As used herein, thecatholyte is the electrolyte in contact with the cathode and configuredto receive anions e.g., hydroxide ions from the cathode upon applicationof a voltage across the cathode and anode. The catholyte is in a cathodecompartment. As used herein, the anolyte is an electrolyte in contactwith the anode and configured to receive cations e.g., protons from theanode upon application of the voltage across the cathode and anode. Theanolyte is in an anode compartment.

In some embodiments of the electrochemical system of FIG. 14, the saltsolution e.g., a sodium chloride solution is placed in a salt solutioncompartment that is separated from the cathode compartment by a cationexchange membrane 206. In some embodiments, as illustrated in FIG. 15,the salt solution is separated from the anolyte compartment by an anionexchange membrane 210. The cathode 201 and the catholyte 202 form thecathode compartment and the anode 204 and the anolyte 203 form the anodecompartment. Alkali 205 is formed in the catholyte 202 and an acid isformed in the anolyte 203.

In one aspect, there is provided a method to produce sodium carbonate,by a) absorbing carbon dioxide in an ammonia solution to form sodiumbicarbonate; and b) subjecting the sodium bicarbonate to anelectrochemical process to produce sodium carbonate wherein theelectrochemical process comprises contacting anode with an anolyte,contacting cathode with a catholyte, and producing a base in thecatholyte and an acid in the anolyte. In one aspect, there is provided amethod to produce sodium carbonate, by a) absorbing carbon dioxide in anammonia solution to form sodium bicarbonate; and b) subjecting thesodium bicarbonate to an electrochemical process to produce sodiumcarbonate wherein the electrochemical process comprises contacting anodewith an anolyte, contacting cathode with a catholyte, producing hydrogengas at the cathode, transferring hydrogen gas from the cathode to theanode, and producing a base in the catholyte and an acid in the anolyte.In some embodiments, the electrochemical process does not compriseproducing a gas such as chlorine gas at the anode. In some embodiments,the electrochemical process comprises producing hydroxide at the cathodeand hydrochloric acid (using sodium chloride as anolyte) or sulfuricacid (using sodium sulfate as anolyte) at the anode.

In one aspect, there is provided a method to modify a Solvay process toproduce a less carbon dioxide intensive Solvay process, by a) absorbingcarbon dioxide in an ammonia solution to form sodium bicarbonate; and b)subjecting the sodium bicarbonate to an electrochemical process toproduce sodium carbonate, thereby resulting in a less carbon dioxideintensive Solvay process wherein the electrochemical process comprisescontacting anode with an anolyte, contacting cathode with a catholyte,and producing a base in the catholyte and an acid in the anolyte. In oneaspect, there is provided a method to modify a Solvay process to producea less carbon dioxide intensive Solvay process, by a) absorbing carbondioxide in an ammonia solution to form sodium bicarbonate; and b)subjecting the sodium bicarbonate to an electrochemical process toproduce sodium carbonate, thereby resulting in a less carbon dioxideintensive Solvay process wherein the electrochemical process comprisescontacting anode with an anolyte, contacting cathode with a catholyte,producing hydrogen gas at the cathode, transferring hydrogen gas fromthe cathode to the anode, and producing a base in the catholyte and anacid in the anolyte. In some embodiments, the electrochemical processdoes not comprise producing a gas such as chlorine gas at the anode. Insome embodiments, the electrochemical process comprises producinghydroxide at the cathode and hydrochloric acid (using sodium chloride asanolyte) or sulfuric acid (using sodium sulfate as anolyte) at theanode.

In some embodiments, the alkaline solution is produced in the catholyteby reducing water at the cathode to hydroxide ions and hydrogen gas inaccordance with Eq. 1, by applying a voltage across the anode andcathode. In some embodiments, concurrent with the production ofhydroxide ions and hydrogen gas at the cathode, at the anode hydrogen isoxidized to protons in accordance with Eq. 2:

At the cathode: 2H₂O+2e ⁻→H₂+2OH⁻  Eq. 1

At the anode: H₂→2H⁺+2e ⁻  Eq. 2

In some embodiments, on applying the voltage across the anode andcathode, hydroxide ions produced at the cathode migrate into thecatholyte to produce the alkaline solution e.g., sodium hydroxidesolution by combining with cations e.g., sodium ions in the catholyte.Concurrently, in some embodiments, under the applied voltage across theanode and cathode, the protons formed at the anode in accordance withEq. 2 migrate into the anolyte and combine with anions in the anolytee.g., chloride ions to produce an acid, e.g., hydrochloric acid in theanolyte. In some embodiments, the anions, e.g., chloride ions aremigrated into the anolyte through the anion exchange membrane from thesalt solution.

In some embodiments, hydrogen produced at the cathode is collected anddirected to the anode for oxidation to protons as in Eq. 2. In someembodiments, since the hydrogen from the cathode is circulated to theanode therefore the need for externally produced hydrogen is reducedthereby reducing the overall energy expended in producing the alkalinesolution. This type of the electrochemical cell and system, where thehydrogen gas is transferred from the cathode to the anode, has beendescribed as ABLE in the provisional application to which priority hasbeen claimed.

In some embodiments, the alkaline solution formed in the catholyte maybe used to regenerate ammonia from the spent ammonia solution (used forsequestering carbon dioxide gas). In some embodiments, the alkalinesolution may be also used to sequester carbon dioxide by absorbing thecarbon dioxide in the catholyte in the cathode compartment or byabsorbing the carbon dioxide in a gas absorber operatively connected tothe cathode compartment configured to receive the catholyte and producea carbonate or bicarbonate solution.

In one aspect, there is provided a method to produce sodium carbonate,by a) absorbing carbon dioxide in an ammonia solution to form sodiumbicarbonate; b) subjecting the sodium bicarbonate to an electrochemicalprocess to produce sodium carbonate wherein the electrochemical processcomprises contacting anode with an anolyte, contacting cathode with acatholyte, and producing a base in the catholyte and an acid in theanolyte; and c) regenerating the ammonia solution using calcium oxideobtained by lime calcinations or regenerating the ammonia solution usingsodium hydroxide obtained from the electrochemical process. In oneaspect, there is provided a method to produce sodium carbonate, by a)absorbing carbon dioxide in an ammonia solution to form sodiumbicarbonate; b) subjecting the sodium bicarbonate to an electrochemicalprocess to produce sodium carbonate wherein the electrochemical processcomprises contacting anode with an anolyte, contacting cathode with acatholyte, producing hydrogen gas at the cathode, transferring hydrogengas from the cathode to the anode, and producing a base in the catholyteand an acid in the anolyte; and c) regenerating the ammonia solutionusing calcium oxide obtained by lime calcinations or regenerating theammonia solution using sodium hydroxide obtained from theelectrochemical process. In some embodiments, the electrochemicalprocess does not comprise producing a gas such as chlorine gas at theanode. In some embodiments, the electrochemical process comprisesproducing hydroxide at the cathode and hydrochloric acid (using sodiumchloride as anolyte) or sulfuric acid (using sodium sulfate as anolyte)at the anode.

In one aspect, there is provided a method to modify a Solvay process toproduce a less carbon dioxide intensive Solvay process, by a) absorbingcarbon dioxide in an ammonia solution to form sodium bicarbonate; b)subjecting the sodium bicarbonate to an electrochemical process toproduce sodium carbonate, thereby resulting in a less carbon dioxideintensive Solvay process wherein the electrochemical process comprisescontacting anode with an anolyte, contacting cathode with a catholyte,and producing a base in the catholyte and an acid in the anolyte; and c)regenerating the ammonia solution using calcium oxide obtained by limecalcinations or regenerating the ammonia solution using sodium hydroxideobtained from the electrochemical process. In one aspect, there isprovided a method to modify a Solvay process to produce a less carbondioxide intensive Solvay process, by a) absorbing carbon dioxide in anammonia solution to form sodium bicarbonate; b) subjecting the sodiumbicarbonate to an electrochemical process to produce sodium carbonate,thereby resulting in a less carbon dioxide intensive Solvay processwherein the electrochemical process comprises contacting anode with ananolyte, contacting cathode with a catholyte, producing hydrogen gas atthe cathode, transferring hydrogen gas from the cathode to the anode,and producing a base in the catholyte and an acid in the anolyte; and c)regenerating the ammonia solution using calcium oxide obtained by limecalcinations or regenerating the ammonia solution using sodium hydroxideobtained from the electrochemical process. In some embodiments, theelectrochemical process does not comprise producing a gas such aschlorine gas at the anode. In some embodiments, the electrochemicalprocess comprises producing hydroxide at the cathode and hydrochloricacid (using sodium chloride as anolyte) or sulfuric acid (using sodiumsulfate as anolyte) at the anode.

In some embodiments of the system of FIG. 16, the alkaline solution 205is produced wherein the catholyte 202 is separated from the anolyte 203by a cation exchange membranes 206 and an anion exchange membrane 210for cations to migrate from salt solution into the catholyte 202 throughthe cation exchange membrane 206 to produce the alkaline solution 205 inthe catholyte 202, and for anions to migrate across an anion exchangemembrane 210 to produce an acid in the anolyte 203. The ion exchangemembranes comprising a cation exchange membrane separates the catholytein the cathode compartment from a third electrolyte. In variousembodiments, the ion exchange membrane comprises an anion exchangemembrane separating the anolyte from the third electrolyte. In variousembodiments, the third electrolyte comprises sodium ions and chlorideions; the system is configured to migrate sodium ions from the thirdelectrolyte to catholyte through the cation exchange membrane, andmigrate chloride ions from the third electrolyte to the anolyte throughthe anion exchange membrane.

In some embodiments, the systems described herein may include a secondcation exchange membrane (not shown in figures) that is in contact withthe anode. In some embodiments, there may be an additional chamberbetween the anion exchange membrane and the anode, such as, a gasdiffusion anode (not shown in Figs). The liquid chamber is in closecontact with the anode and the anion exchange membrane which anionexchange membrane is further in contact with the center saltcompartment.

As disclosed in U.S. Provisional Patent Application No. 61/081,299,filed 16 Jul. 2008, titled, “Low Energy pH Modulation for CarbonSequestration Using Hydrogen Absorptive Metal Catalysts,” hereinincorporated by reference in its entirety, in various embodiments, theanode and the cathode of the present system may comprise a noble metal,a transition metal, a platinum group metal, a metal of Groups IVB, VB,VIB, or VIII of the periodic table of elements, alloys of these metals,or oxides of these metals. Exemplary materials include palladium,platinum, iridium, rhodium, ruthenium, titanium, zirconium, chromium,iron, cobalt, nickel, palladium-silver alloys, and palladium-copperalloys. In various embodiments, the cathode and/or the anode may becoated with a reactive coating comprising a metal, a metal alloy, or anoxide, formed by sputtering, electroplating, vapor deposition, or anyconvenient method of producing a layer of reactive coating on thesurface of the cathode and/or anode. In other embodiments, the cathodeand/or the anode may comprise a coating designed to provide selectivepenetration and/or release of certain chemicals or hydroxide ions and/oranti-fouling protection. Exemplary coatings include non-metallicpolymers; in specific embodiments herein, an anode fabricated from a20-mesh Ni gauze material, and a cathode fabricated from a 100-mesh Ptgauze material was used.

Reduction of water at the cathode produces hydroxide ions that migrateinto the catholyte. The production of hydroxide ions in the catholytesurrounding the cathode may increase the pH of the catholyte. In variousembodiments, the solution with the elevated pH is used in situ, or isdrawn off and utilized in a separate reaction, e.g., to react withsodium bicarbonate as described herein. Depending on the balance of therate of hydroxide ion production versus the rate of carbonate formationin the catholyte, it is possible for the pH to remain the same or evendecrease, as hydroxide ions are consumed in the reaction.

Oxidation of hydrogen gas at the anode results in production of hydrogenions at the anode that desorb from the structure of the anode andmigrate into the electrolyte surrounding the anode, resulting in alowering of the pH of the anolyte. Thus, the pH of the electrolytes inthe system can be adjusted by controlling the voltage across the cathodeand anode and using electrodes comprised of a material capable ofabsorbing or desorbing hydrogen ions. In various embodiments, theprocess generates hydroxide ions in solution with less than a 1:1 ratioof CO₂ molecules released into the environment per hydroxide iongenerated. In various embodiments, the anolyte enriched with hydrogenions (i.e. an acid), can be utilized for a variety of applicationsincluding dissolving minerals to produce a solution of divalent cations(e.g. calcium and/or magnesium ions) for use in generatingcarbonate/bicarbonate products.

In one aspect, there is provided a system comprising a Solvay systemintegrated with an electrochemical system, comprising a) a Solvay systemcomprising an absorber configured to absorb carbon dioxide in an ammoniasolution to form sodium bicarbonate; and b) a first electrochemicalsystem operably connected to the Solvay system configured to convert thesodium bicarbonate to sodium carbonate wherein the electrochemicalsystem comprises an anode in contact with an anolyte, a cathode incontact with a catholyte; one or more of ion exchange membrane; and ahydrogen gas delivery system operably connected to the cathodecompartment and configured to transfer hydrogen gas from the cathode tothe anode.

In one aspect, there is provided a system comprising a Solvay systemintegrated with an electrochemical system, comprising a) a Solvay systemcomprising an absorber configured to absorb carbon dioxide in an ammoniasolution to form sodium bicarbonate; b) a first electrochemical systemoperably connected to the Solvay system configured to convert the sodiumbicarbonate to sodium carbonate wherein the electrochemical systemcomprises an anode in contact with an anolyte, a cathode in contact witha catholyte; one or more of ion exchange membrane; and a hydrogen gasdelivery system operably connected to the cathode compartment andconfigured to transfer hydrogen gas from the cathode to the anode; andc) a regenerator operably connected to the Solvay system configured toregenerate the ammonia solution after absorption of the carbon dioxidein the ammonia solution.

In one aspect, there is provided a system comprising a Solvay systemintegrated with an electrochemical system, comprising a) a Solvay systemcomprising an absorber configured to absorb carbon dioxide in an ammoniasolution to form sodium bicarbonate; b) a first electrochemical systemoperably connected to the Solvay system configured to convert the sodiumbicarbonate to sodium carbonate wherein the electrochemical systemcomprises an anode in contact with an anolyte, a cathode in contact witha catholyte; one or more of ion exchange membrane; and a hydrogen gasdelivery system operably connected to the cathode compartment andconfigured to transfer hydrogen gas from the cathode to the anode; c) aregenerator operably connected to the Solvay system configured toregenerate the ammonia solution after absorption of the carbon dioxidein the ammonia solution; and d) a lime calciner operably connected tothe regenerator and configured to produce calcium oxide for regeneratingthe ammonia solution.

In one aspect, there is provided a system comprising a Solvay systemintegrated with an electrochemical system, comprising a) a Solvay systemcomprising an absorber configured to absorb carbon dioxide in an ammoniasolution to form sodium bicarbonate; b) a first electrochemical systemoperably connected to the Solvay system configured to convert the sodiumbicarbonate to sodium carbonate wherein the electrochemical systemcomprises an anode in contact with an anolyte, a cathode in contact witha catholyte; one or more of ion exchange membrane; and a hydrogen gasdelivery system operably connected to the cathode compartment andconfigured to transfer hydrogen gas from the cathode to the anode; c) aregenerator operably connected to the Solvay system configured toregenerate the ammonia solution after absorption of the carbon dioxidein the ammonia solution; and d) a second electrochemical system operablyconnected to the regenerator and configured to produce sodium hydroxidefor regenerating the ammonia solution.

The first and second electrochemical processes and/or first and secondelectrochemical systems, as described herein, may be the sameelectrochemical systems and process or may be different electrochemicalprocesses and systems. For example, in some embodiments, the firstelectrochemical process and system may be the one described in FIG. 13and the second electrochemical process and system may be the onedescribed in FIG. 14, or vice versa. For example, in some embodiments,the first electrochemical process and system may be the one described inFIG. 14 and the second electrochemical process and system may be the onedescribed in FIG. 15, or vice versa. For example, in some embodiments,the first electrochemical process and system may be the one described inFIG. 15 and the second electrochemical process and system may be the onedescribed in FIG. 16, or vice versa. For example, in some embodiments,the first electrochemical process and system may be the same such as theone described in FIG. 13, 14, 15, or 16.

In some embodiments, the system includes an inlet system configured todeliver sodium bicarbonate solution (e.g. solution containingbicarbonate/carbonate ions obtained by absorbing carbon dioxide gas withammonia solution) into the catholyte compartment. In some embodiments,the cathode compartment of the electrochemical system is operablyconnected to an absorber that contains ammonia and is connected tocarbon dioxide obtained from Solvay process or from any other plant,such as steel, cement, or power plant. The ammonia solution in theabsorber after absorbing the carbon dioxide forms a carbon dioxidecharged solution containing bicarbonate and/or carbonate ions and aspent ammonia (such as ammonium chloride). This bicarbonate and/orcarbonate ion containing solution may then be transferred to the cathodecompartment of the electrochemical system where the sodium hydroxidegenerated by the cathode may convert the remaining bicarbonate to sodiumcarbonate resulting in soda ash formation. This type of theelectrochemical cell and system has been described as ABLE-C in theprovisional application to which priority has been claimed. In someembodiments, the sodium bicarbonate solution from the absorber may becontacted with the sodium hydroxide from the electrochemical cell,outside the electrochemical cell, such that the sodium bicarbonatesolution is not administered to the cathode compartment. As such,similar reaction takes place between the sodium bicarbonate from theabsorber and sodium hydroxide from the catholyte to form sodiumcarbonate.

As illustrated in FIG. 17, a first electrochemical process 400 of FIG.16 is operably connected to the absorber 500 of the Solvay system. Theammonia solution in the absorber 500 absorbs carbon dioxide gas anddissolves it to form sodium bicarbonate solution (this solution maycontain sodium carbonate too). The sodium bicarbonate solution may bethen added to the cathode compartment of the first electrochemicalprocess where the hydroxide ions generated at the cathode convert sodiumbicarbonate to sodium carbonate (soda ash). As noted above, in someembodiments, the sodium bicarbonate solution may be contacted with thesodium hydroxide from the catholyte outside the electrochemical cell(not shown in the figure). The spent ammonia in the absorber (e.g.,NH₄Cl) may be then treated with sodium hydroxide generated at thecathode in the second electrochemical process, to regenerate ammoniasolution. The regenerated ammonia may be transferred back to theabsorber 500. The first and the second electrochemical systems may besame (as illustrated in FIG. 17) or may be different, as describedherein.

In various embodiments, the absorber includes a gas mixer/gas absorberthat enhances the absorption of CO₂ in ammonia. In one embodiment, thegas mixer/gas absorber includes a series of spray nozzles that produce aflat sheet or curtain of liquid through which the gas is directed forabsorption; in another embodiment the gas mixer/gas absorber includesspray absorber that creates a mist into which the gas is directed forabsorption; other commercially available gas/liquid absorber e.g., anabsorber available from Neumann Systems, Colorado, USA may be used. Inoperation, the cathode and anode compartments are filled withelectrolytes and a voltage is applied across the cathode and anode. Invarious embodiments, the voltage is adjusted to a level to causeproduction of hydrogen gas at the cathode without producing a gas, e.g.,chlorine or oxygen, at the anode. In various embodiments, the systemincludes a cathode and an anode that facilitate reactions whereby thecatholyte is enriched with hydroxide ions and the anolyte is enrichedwith hydrogen ions.

In various embodiments, a conductive electrolyte solution can beemployed as the electrolyte solution within the reservoir and in someembodiments the electrolyte solution comprises seawater, brine, orbrackish water.

As disclosed herein, in various embodiments, hydroxide ions are producedin the catholyte by applying a relatively low voltage, e.g., less than3.0 V, such as less than 2.0 V, or less than 1.0 V or less than 0.8 V orless than 0.6 V or less than 0.4 V across the cathode and anode. Invarious embodiments, hydroxide ions are produced from water in thecatholyte in contact with the cathode, and carbonate ions are producedin the catholyte by dissolving sodium bicarbonate solution in thecatholyte in the catholyte compartment. In some embodiments, theelectrochemical system comprises a hydrogen gas delivery systemconfigured to direct hydrogen gas produced at the cathode to the anode.

In some embodiments, the catholyte is operatively connected to theabsorber configured to dissolve carbon dioxide in ammonia; the system isconfigured to produce a pH differential (ΔpH) between 0 and 14 orgreater between the anolyte and catholyte. For example, ΔpH may be zerowhen the catholyte and anolyte are of equal pH, or ΔpH may be 14 whenthe catholyte is pH 14 and the anolyte is pH 0. As such, ΔpH between theanolyte and catholyte may be greater than 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, or 13; ΔpH between the anolyte and catholyte may be lessthan 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1. By the method,acid produced in the anolyte is utilized to dissolve a mafic mineraland/or a cellulose material.

In various embodiments, a gas, e.g., oxygen or chlorine is not producedat the anode; in various embodiments, hydrogen gas from an externalsource is provided to the anode where it is oxidized to hydrogen ionsthat migrate into the anolyte to produce an acid in the anolyte.

In various embodiments, hydroxide ions produced at the cathode in thesecond catholyte compartment migrate into the catholyte and may causethe pH of the catholyte to adjust, e.g., the pH of the catholyte mayincrease, decrease or remain the same, depending on the rate of removalof catholyte from the system. In various embodiments, the pH of thecatholyte is adjusted by producing hydroxide ions from water at thecathode, and allowing the hydroxide ions to migrate into the catholyte.The pH is also adjusted by dissolving sodium bicarbonate solution in thecatholyte to produce carbonate ions.

In some embodiments, the overall cell potential of the system can bedetermined through the Gibbs energy change of the reaction by theformula:

E _(cell) =−ΔG/nF

Or, at standard temperature and pressure conditions:

E° _(cell) =−ΔG°/nF

where, Ecell is the cell voltage, ΔG is the Gibbs energy of reaction, nis the number of electrons transferred, and F is the Faraday constant(96485 J/V·mol). The Ecell of each of these reactions is pH dependentbased on the Nernst equation.

The overall cell potential can be determined through the combination ofNernst equations for each half cell reaction:

E=E°−RT ln(Q)/nF

where, E° is the standard reduction potential, R is the universal gasconstant, (8.314 J/mol K) T is the absolute temperature, n is the numberof electrons involved in the half cell reaction, F is Faraday's constant(96485 J/V mol), and Q is the reaction quotient such that:

E _(total) =E _(cathode) +E _(anode)

When hydrogen is oxidized to protons at the anode as follows:

H₂=2H⁺+2e ⁻,

E° is 0.00 V, n is 2, and Q is the square of the activity of H+ so that:

E _(anode)=+0.059pH _(a),

where pH_(a) is the pH of the anolyte.

When water is reduced to hydroxide ions and hydrogen gas at the cathodeas follows:

2H₂O+2e ⁻=H₂+2OH⁻,

E° is −0.83 V, n is 2, and Q is the square of the activity of OH— sothat:

E _(cathode)=−0.059pH _(c),

where pH_(c) is the pH of the catholyte.

Therefore, the E for the cathode and anode reactions varies with the pHof the anode and catholytes. Thus, if the anode reaction, which isoccurring in an acidic environment, is at a pH of 0, then the E of thereaction is 0 V for the half cell reaction. For the cathode reaction, ifthe generation of bicarbonate ions occur at a pH of 7, then thetheoretical E is 7×(−0.059 V)=−0.413 V for the half cell reaction wherea negative E means energy is needed to be input into the half cell orfull cell for the reaction to proceed. Thus, if the anode pH is 0 andthe cathode pH is 7 then the overall cell potential would be 0.413 V,where:

E _(total)=−0.059(pH _(a) −pH _(c))=−0.059ΔpH.

Embodiments in which carbonate ions are produced, if the anode pH is 0and the cathode pH is 10, this would represent an E of 0.59 V.

Thus, in various embodiments, directing bicarbonate solution into thecatholyte may lower the pH of the catholyte by producing carbonate ionsin the catholyte, and also lower the voltage across the anode andcathode to produce hydroxide, carbonate and/or bicarbonate in thecatholyte. Thus, operation of the electrochemical cell with the cathodepH at 7 or greater may provide a significant energy savings.

In various embodiments, for different pH values in the catholyte and theanolyte, hydroxide ions, carbonate ions and/or bicarbonate ions areproduced in the catholyte when the voltage applied across the anode andcathode was less than 3.0 V, 2.9 V, 2.8 V, 2.7 V, 2.6 V, 2.5 V, 2.4 V,2.3 V, 2.2 V, 2.1 V, 2.0 V, 1.9 V, 1.8 V, 1.7 V, 1.6 V, 1.5 V, 1.4 V,1.3 V, 1.2 V, 1.1 V, 1.0 V, 0.9 V, 0.8 V, 0.7 V, 0.6 V, 0.5 V, 0.4 V,0.3 V, 0.2 V, or 0.1 V. For selected voltages in the above range, the pHdifferential (ΔpH) between the anolyte and the catholyte may be between0 and 14 or greater. For example, ΔpH may be zero when the catholyte andanolyte are of equal pH, or ΔpH may be 14 when the catholyte is pH 14and the anolyte is pH 0. As such, ΔpH between the anolyte and catholytemay be greater than 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13; ΔpHbetween the anolyte and catholyte may be less than 14, 13, 12, 11, 10,9, 8, 7, 6, 5, 4, 3, 2, or 1.

In various embodiments, the system and method are configurable forbatch, semi-batch or continuous flow operation with or without theoption to withdraw portions of the sodium hydroxide produced in thecatholyte, or withdraw all or a portions of the acid produced in theanolyte, or direct the hydrogen gas produced at the cathode to the anodewhere it may be oxidized.

In various embodiments, hydroxide ions, bicarbonate ions and/orcarbonate ion solutions are produced in the catholyte when the voltageapplied across the anode and cathode is less than 3.0 V, 2.9 V or less,2.8 V or less, 2.7 V or less, 2.6 V or less, 2.5 V or less, 2.4 V orless, 2.3 V or less, 2.2 V or less, 2.1 V or less, 2.0 V or less, 1.9 Vor less, 1.8 V or less, 1.7 V or less, 1.6 V, or less 1.5 V or less, 1.4V or less, 1.3 V or less, 1.2 V or less, 1.1 V or less, 1.0 V or less,0.9 V or less or less, 0.8 V or less, 0.7 V or less, 0.6 V or less, 0.5V or less, 0.4 V or less, 0.3 V or less, 0.2 V or less, or 0.1 V orless.

In another embodiment, the voltage across the anode and cathode can beadjusted such that gas will form at the anode, e.g., oxygen or chlorine,while hydroxide ions, carbonate ions and bicarbonate ions are producedin the catholyte and hydrogen gas is generated at the cathode. However,in this embodiment, hydrogen gas is not supplied to the anode. As can beappreciated by one ordinarily skilled in the art, in this embodiment,the voltage across the anode and cathode will be higher compared to theembodiment when a gas does not form at the anode.

The anion exchange membrane and the cation exchange membrane, asdescribed herein, can be conventional ion exchange membranes. In someembodiments, the membranes are capable of functioning in an acidicand/or basic electrolytic solution and exhibit high ion selectivity, lowionic resistance, high burst strength, and high stability in an acidicelectrolytic solution in a temperature range of 0° C. to 100° C. orhigher. In some embodiments a membrane stable in the range of 0° C. to80° C., or 0° C. to 90° C., but not stable above these ranges may beused. Suitable membranes include a Teflon™-based cation exchangemembrane available from Asahi Kasei of Tokyo, Japan. However, low costhydrocarbon-based cation exchange membranes can also be utilized, e.g.,the hydrocarbon-based membranes available from, e.g., MembraneInternational of Glen Rock, N.J., and USA.

In some embodiments, the electrolyte including the catholyte or thecathode electrolyte and/or the anolyte or the anode electrolyte, or thethird electrolyte disposed between AEM and CEM, in the systems andmethods provided herein include, but not limited to, saltwater or freshwater. The saltwater includes, but is not limited to, seawater, brine,and/or brackish water. “Saltwater” is employed in its conventional senseto refer to a number of different types of aqueous fluids, where theterm “saltwater” includes, but is not limited to, brackish water, seawater and brine (including, naturally occurring subterranean brines oranthropogenic subterranean brines and man-made brines, e.g., geothermalplant wastewaters, desalination waste waters, etc), as well as othersalines having a salinity that is greater than that of freshwater. Brineis water saturated or nearly saturated with salt and has a salinity thatis 50 ppt (parts per thousand) or greater. Brackish water is water thatis saltier than fresh water, but not as salty as seawater, having asalinity ranging from 0.5 to 35 ppt. Seawater is water from a sea orocean and has a salinity ranging from 35 to 50 ppt. The saltwater sourcemay be a naturally occurring source, such as a sea, ocean, lake, swamp,estuary, lagoon, etc., or a man-made source. In some embodiments, thesystems provided herein include the saltwater from terrestrial brine. Insome embodiments, the depleted saltwater withdrawn from theelectrochemical cells is replenished with salt and re-circulated back inthe electrochemical cell.

In some embodiments, the electrolyte including the cathode electrolyteand/or the anode electrolyte and/or the third electrolyte, such as,saltwater includes water containing more than 1% chloride content, suchas, NaCl; or more than 10% NaCl; or more than 20% NaCl; or more than 30%NaCl; or more than 40% NaCl; or more than 50% NaCl; or more than 60%NaCl; or more than 70% NaCl; or more than 80% NaCl; or more than 90%NaCl; or between 1-99% NaCl; or between 1-95% NaCl; or between 1-90%NaCl; or between 1-80% NaCl; or between 1-70% NaCl; or between 1-60%NaCl; or between 1-50% NaCl; or between 1-40% NaCl; or between 1-30%NaCl; or between 1-20% NaCl; or between 1-10% NaCl; or between 10-99%NaCl; or between 10-95% NaCl; or between 10-90% NaCl; or between 10-80%NaCl; or between 10-70% NaCl; or between 10-60% NaCl; or between 10-50%NaCl; or between 10-40% NaCl; or between 10-30% NaCl; or between 10-20%NaCl; or between 20-99% NaCl; or between 20-95% NaCl; or between 20-90%NaCl; or between 20-80% NaCl; or between 20-70% NaCl; or between 20-60%NaCl; or between 20-50% NaCl; or between 20-40% NaCl; or between 20-30%NaCl; or between 30-99% NaCl; or between 30-95% NaCl; or between 30-90%NaCl; or between 30-80% NaCl; or between 30-70% NaCl; or between 30-60%NaCl; or between 30-50% NaCl; or between 30-40% NaCl; or between 40-99%NaCl; or between 40-95% NaCl; or between 40-90% NaCl; or between 40-80%NaCl; or between 40-70% NaCl; or between 40-60% NaCl; or between 40-50%NaCl; or between 50-99% NaCl; or between 50-95% NaCl; or between 50-90%NaCl; or between 50-80% NaCl; or between 50-70% NaCl; or between 50-60%NaCl; or between 60-99% NaCl; or between 60-95% NaCl; or between 60-90%NaCl; or between 60-80% NaCl; or between 60-70% NaCl; or between 70-99%NaCl; or between 70-95% NaCl; or between 70-90% NaCl; or between 70-80%NaCl; or between 80-99% NaCl; or between 80-95% NaCl; or between 80-90%NaCl; or between 90-99% NaCl; or between 90-95% NaCl. In someembodiments, the above recited percentages apply to sodium sulfate as anelectrolyte.

In some embodiments, the cathode compartment may also be operativelyconnected to a waste gas treatment system (not illustrated) where thebase solution produced in the catholyte is utilized, e.g., to sequestercarbon dioxide contained in the waste gas by contacting the waste gasand the catholyte with a solution of divalent cations to precipitatehydroxides, carbonates and/or bicarbonates as described in U.S. patentapplication Ser. No. 12/344,019, filed 24 Dec. 2008, which isincorporated herein by reference in its entirety.

In some embodiments, the sodium carbonate (soda ash) may be treated withdivalent cations, such as calcium or magnesium ions, to precipitatecalcium and magnesium carbonates which may be utilized as buildingmaterials, e.g., as cements and aggregates, as described in U.S. patentapplication Ser. No. 12/126,776, filed 23 May 2008, which isincorporated herein by reference in its entirety. In some embodiments,some or all of the carbonates and/or bicarbonates are allowed to remainin an aqueous medium, e.g., a slurry or a suspension, and are disposedof in an aqueous medium, e.g., in the ocean depths.

In some embodiments, the cathode and anode are also operativelyconnected to an off-peak electrical power-supply system that suppliesoff-peak voltage to the electrodes. Since the cost of off-peak power islower than the cost of power supplied during peak power-supply times,the system can utilize off-peak power to produce a base solution in thecatholyte at a relatively lower cost.

In some embodiments, partially desalinated water is produced in thethird electrolyte as a result of migration of cations and anions fromthe third electrolyte to the adjacent anolyte and catholyte. In variousembodiments, the partially desalinated water is operatively connected toa desalination system (not illustrated) where it is further desalinatedas described in U.S. patent application Ser. No. 12/163,205, filed 27Jun. 2008, which is incorporated herein by reference in its entirety.

In some embodiments, the system produces an acid, e.g., hydrochloricacid in the anolyte. In some embodiments, the anode compartment isoperably connected to a system for dissolving minerals and wastematerials comprising divalent cations to produce a solution of divalentcations, e.g., Ca²⁺ and Mg²⁺. In some embodiments, the divalent cationsolution may be utilized to precipitate divalent carbonates and/orbicarbonates by contacting the divalent cation solution with sodiumcarbonate solution. In various embodiments, the precipitates are used asbuilding materials e.g., cement and aggregates as described in U.S.patent application Ser. No. 12/126,776, which is incorporated herein byreference in its entirety.

In some embodiments, the system includes a catholyte withdrawal andreplenishing system (not illustrated) capable of withdrawing all of, ora portion of, the catholyte from the cathode compartment. In someembodiments, the system also includes a salt solution supply system (notshown) for providing a salt solution, e.g., concentrated sodiumchloride, as the third electrolyte. In some embodiments, the system alsoincludes inlet ports (not shown) for introducing fluids into the cellsand outlet ports (not shown) for removing fluids from the cells.

In the present system since a gas does not form at the anode, the systemmay produce hydroxide ions in the catholyte and hydrogen gas at thecathode and hydrogen ions at the anode when less than 2.0 V is appliedacross the anode and cathode, in contrast to the higher voltage that isrequired when a gas is generated at the anode, e.g., chlorine or oxygen.As will be appreciated by one ordinarily skilled in the art, by notforming a gas at the anode and by providing hydrogen gas to the anodefor oxidation at the anode, and by otherwise controlling the resistancein the system for example by decreasing the electrolyte path lengths andby selecting ionic membranes with low resistance and any other methodknow in the art, hydroxide ions can be produced in the catholyte withthe present lower voltages.

In various embodiments, depending on the ionic species desired in thesystem, alternative reactants can be utilized. Thus, for example, if apotassium salt such as potassium hydroxide or potassium carbonate isdesired in the cathode electrolyte, then a potassium salt such aspotassium chloride can be utilized as an electrolyte. Similarly, ifsulfuric acid is desired in the anolyte, then a sulfate such as sodiumsulfate can be utilized in electrolyte.

In some embodiments, the system and method described herein areintegrated with a carbonate and/or bicarbonate precipitation systemwherein a solution of divalent cations, when added to the catholytecontaining sodium carbonate, causes formation of precipitates ofdivalent carbonate and/or bicarbonate compounds, e.g., calcium carbonateor magnesium carbonate and/or their bicarbonates. In variousembodiments, the precipitated divalent carbonate and/or bicarbonatecompounds may be utilized as building materials, e.g., cements andaggregates as described for example in U.S. patent application Ser. No.12/126,776, filed 23 May 2008, which is incorporated herein by referencein its entirety.

In some embodiments, the system and method described herein areintegrated with a mineral and/or material dissolution and recoverysystem (not illustrated) wherein the acidic anolyte solution is utilizedto dissolve calcium and/or magnesium-rich minerals e.g., serpentine orolivine, or waste materials, e.g., fly ash, red mud and the like, toform divalent cation solutions that may be utilized, e.g., toprecipitate carbonates and/or bicarbonates as described herein.

In some embodiments, the system and method described herein areintegrated with an aqueous desalination system (not illustrated) whereinthe partially desalinated water of the third electrolyte of the systemis used as feed-water for the desalination system, as described in U.S.patent application Ser. No. 12/163,205, filed 27 Jun. 2008, which isincorporated herein by reference in its entirety.

In some embodiments, the system and method described herein areintegrated with a carbonate and/or bicarbonate solution disposal system(not illustrated) wherein, rather than producing precipitates bycontacting a solution of divalent cations with sodium carbonate to formprecipitates, the system produces a slurry or suspension comprisingcarbonates and/or bicarbonates. In various embodiments, the slurry orsuspension is disposed of in a location where it is held stable for anextended periods of time, e.g., the slurry/suspension is disposed in anocean at a depth where the temperature and pressure are sufficient tokeep the slurry stable indefinitely, as described in U.S. patentapplication Ser. No. 12/344,019, filed 24 Dec. 2008, which is hereinincorporated by reference in its entirety.

In some embodiments, the systems provided herein may include a processorto process the compositions containing bicarbonate and/or carbonateproducts. An illustrative example of the processor is described in FIG.18. For example, in some embodiments, the processor includes a reactorconfigured to react soda ash obtained from the electrochemical system(such as FIGS. 13-17 described herein) with divalent cations from asource of divalent cations to produce compositions containingcarbonate/bicarbonate products. In some embodiments, the processor mayfurther comprise a settling tank configured for settling compositions.The processor may further comprise a treatment system configured toconcentrate compositions comprising carbonates, bicarbonates, orcarbonates and bicarbonates and produce a supernatant; however, in someembodiments the compositions may be used without further treatment. Forexample, systems may be configured to directly use compositions from thereactor (optionally with minimal post-processing) in the manufacture ofbuilding materials. In another non-limiting example, systems may beconfigured to directly inject compositions from the processor(optionally with minimal post-processing) into a subterranean site asdescribed in U.S. Provisional Patent Application No. 61/232,401, filed 7Aug. 2009, which is incorporated herein by reference in its entirety.The source of divalent cations may be from any of a variety of sourcesof divalent cations, including, but not limited to, seawater, brines,and freshwater with added minerals. In some embodiments, the source ofdivalent cations comprises divalent cations of alkaline earth metals(e.g., Ca²⁺, Mg²⁺).

The treatment system may comprise a liquid-solid separator or some otherdewatering system configured to treat processor-produced compositions toproduce supernatant and concentrated compositions (e.g., concentratedwith respect to carbonates and/or bicarbonates). The treatment systemmay further comprise a filtration system, wherein the filtration systemcomprises at least one filtration unit configured for filtration ofsupernatant from the dewatering system, filtration of the compositionfrom the processor, or a combination thereof. For example, in someembodiments, the filtration system comprises one or more filtrationunits selected from a microfiltration unit, an ultrafiltration unit, ananofiltration unit, and a reverse osmosis unit. In some embodiments,the processing system comprises a nanofiltration unit configured toincrease the concentration of divalent cations in the retentate andreduce the concentration of divalent cations in the filtrate. In suchembodiments, nanofiltration unit retentate may be recirculated to aprocessor of the system for producing compositions described herein.

In some embodiments, the calcium carbonate composition formed by theprocesses described herein comprises vaterite, aragonite, amorphouscalcium carbonate, calcite, or combination thereof. In some embodiments,such calcium carbonate (optionally containing magnesium carbonate) formsa cementitious material. The cementitous composition has elements ormarkers that originate from the carbon from the source of carbon used inthe process. The composition after setting, and hardening has acompressive strength of at least 14 MPa; or at least 16 MPa; or at least18 MPa; or at least 20 MPa; or at least 25 MPa; or at least 30 MPa; orat least 35 MPa; or at least 40 MPa; or at least 45 MPa; or at least 50MPa; or at least 55 MPa; or at least 60 MPa; or at least 65 MPa; or atleast 70 MPa; or at least 75 MPa; or at least 80 MPa; or at least 85MPa; or at least 90 MPa; or at least 95 MPa; or at least 100 MPa; orfrom 14-100 MPa; or from 14-80 MPa; or from 14-75 MPa; or from 14-70MPa; or from 14-65 MPa; or from 14-60 MPa; or from 14-55 MPa; or from14-50 MPa; or from 14-45 MPa; or from 14-40 MPa; or from 14-35 MPa; orfrom 14-30 MPa; or from 14-25 MPa; or from 14-20 MPa; or from 14-18 MPa;or from 14-16 MPa; or from 17-35 MPa; or from 17-30 MPa; or from 17-25MPa; or from 17-20 MPa; or from 17-18 MPa; or from 20-100 MPa; or from20-90 MPa; or from 20-80 MPa; or from 20-75 MPa; or from 20-70 MPa; orfrom 20-65 MPa; or from 20-60 MPa; or from 20-55 MPa; or from 20-50 MPa;or from 20-45 MPa; or from 20-40 MPa; or from 20-35 MPa; or from 20-30MPa; or from 20-25 MPa; or from 30-100 MPa; or from 30-90 MPa; or from30-80 MPa; or from 30-75 MPa; or from 30-70 MPa; or from 30-65 MPa; orfrom 30-60 MPa; or from 30-55 MPa; or from 30-50 MPa; or from 30-45 MPa;or from 30-40 MPa; or from 30-35 MPa; or from 40-100 MPa; or from 40-90MPa; or from 40-80 MPa; or from 40-75 MPa; or from 40-70 MPa; or from40-65 MPa; or from 40-60 MPa; or from 40-55 MPa; or from 40-50 MPa; orfrom 40-45 MPa; or from 50-100 MPa; or from 50-90 MPa; or from 50-80MPa; or from 50-75 MPa; or from 50-70 MPa; or from 50-65 MPa; or from50-60 MPa; or from 50-55 MPa; or from 60-100 MPa; or from 60-90 MPa; orfrom 60-80 MPa; or from 60-75 MPa; or from 60-70 MPa; or from 60-65 MPa;or from 70-100 MPa; or from 70-90 MPa; or from 70-80 MPa; or from 70-75MPa; or from 80-100 MPa; or from 80-90 MPa; or from 80-85 MPa; or from90-100 MPa; or from 90-95 MPa; or 14 MPa; or 16 MPa; or 18 MPa; or 20MPa; or 25 MPa; or 30 MPa; or 35 MPa; or 40 MPa; or 45 MPa. For example,in some embodiments of the foregoing aspects and the foregoingembodiments, the composition after setting, and hardening has acompressive strength of 14 MPa to 40 MPa; or 17 MPa to 40 MPa; or 20 MPato 40 MPa; or 30 MPa to 40 MPa; or 35 MPa to 40 MPa. In someembodiments, the compressive strengths described herein are thecompressive strengths after 1 day, or 3 days, or 7 days, or 28 days.

In some embodiments, electrochemical cells (e.g., a stack ofelectrochemical cells) may be operably connected to the above describedprocessing system configured to precipitate a precipitation materialcomprising bicarbonates and/or carbonates (or a processed form thereof).Such carbonates and/or bicarbonates comprise calcium and/or magnesium.In some embodiments, the electrochemical cell or the stack ofelectrochemical cells may be operably connected to a system for furtherprocessing of the anolyte, which may comprise hydrochloric acid (ifNaCl(aq) is used) or sulfuric acid (if Na₂SO₄ (aq) is used). Forexample, in some embodiments, the electrochemical cell or the stack ofelectrochemical cells may be operably connected to a mineral-processingsystem comprising a mineral processor configured to dissolve minerals(e.g., mafic minerals such as olivine, serpentine, etc.) with theanolyte (e.g., hydrochloric acid and sodium chloride, sulfuric acid andsodium carbonate, etc.) and produce a solution comprising calcium and/ormagnesium ions. In some embodiments, the anolyte may be used for otherpurposes in addition to, or instead of, mineral dissolution, includinguse as a reactant in production of cellulosic biofuels, use in theproduction of polyvinyl chloride (PVC), and the like. Systemsappropriate for such uses may be operably connected to the stack ofelectrochemical cells, or the anolyte may be transported to anappropriate site for use.

EXAMPLE Example 1

A solvay process is performed by absorbing carbon dioxide into ammoniasolution in sodium chloride. The carbon dioxide is obtained from fluegas emitted by a power plant. The carbon dioxide gas is bubbled into theammonia+sodium chloride solution. The carbon dioxide gas dissolves inthe solution to form sodium bicarbonate and ammonium chloride isgenerated. Sodium bicarbonate is separated from the ammonium solutionand is subjected to the electrochemical process for carbonate formation.

Example 2

This study demonstrates the savings in the voltage when anelectrochemical cell was run with sodium hydroxide as catholyte vs.sodium bicarbonate as catholyte. A voltage sweep was performed in anelectrochemical cell that was containing a 3-cell system (e.g.,electrochemical cell of FIG. 16) with an anode and an anode electrolytein an anode compartment, a cathode and a catholyte in a cathodecompartment, and the anode compartment and the cathode compartmentseparated by an anion exchange membrane and a cation exchange membrane.

In one set of experiment, a voltage sweep was performed in theelectrochemical cell where the anode was in contact with 0.5 wt %hydrochloric acid solution, the cathode was in contact with 10 wt %sodium hydroxide solution, and sodium chloride solution was in themiddle chamber between ion exchange membranes. In another set ofexperiment, a voltage sweep was performed in the electrochemical cellthat was containing anode in contact with 0.5 wt % hydrochloric acidsolution, cathode in contact with 1 mol/L sodium bicarbonate solution(at pH 10), and sodium chloride solution was in the middle chamberbetween ion exchange membranes. The 1 mol/L sodium bicarbonate solutionwas formed by bubbling carbon dioxide in 1 mol sodium hydroxide solutionthat resulted in the formation of 1 mol/L sodium bicarbonate solution.

FIG. 19 illustrates that significant savings in the voltage wereobserved by introducing sodium bicarbonate into the catholyte (˜250 mV)as compared to sodium hydroxide. The sodium hydroxide generated at thecathode converted bicarbonate to carbonate. The conversion ofbicarbonate to carbonate depended on flow rates, current density andlength of time.

While preferred embodiments have been shown and described herein, itwill be obvious to those skilled in the art that such embodiments areprovided by way of example only. Numerous variations, changes, andsubstitutions will now occur to those skilled in the art. It should beunderstood that various alternatives to the embodiments described hereinmay be employed without departing from spirit of this specification. Itis intended that the following claims define the scope of the inventionand that methods and structures within the scope of these claims andtheir equivalents be covered thereby.

1. A method to produce sodium carbonate, comprising: a) absorbing carbondioxide in an ammonia solution to form sodium bicarbonate; and b)subjecting the sodium bicarbonate to a first electrochemical process toproduce sodium carbonate.
 2. A method to modify a Solvay process toproduce a less carbon dioxide intensive Solvay process, comprising: a)absorbing carbon dioxide in an ammonia solution to form sodiumbicarbonate; and b) subjecting the sodium bicarbonate to a firstelectrochemical process to produce sodium carbonate, thereby resultingin a less carbon dioxide intensive Solvay process.
 3. The method ofclaim 1 or 2, further comprising regenerating the ammonia solution usingcalcium oxide obtained by lime calcination.
 4. The method of claim 1 or2, further comprising regenerating the ammonia solution using sodiumhydroxide obtained from the first or a second electrochemical process.5. The method of claim 1 or 2, wherein the method does not comprisebicarbonate calcination, lime calcination, or a combination thereof. 6.The method of claim 1 or 2, wherein the method produces less than 80%carbon dioxide as compared to a conventional Solvay process.
 7. Themethod of claim 1 or 2, further comprising treating the sodium carbonatewith calcium or magnesium ions to form calcium carbonate, magnesiumcarbonate, or combination thereof.
 8. The method of claim 7, wherein thecalcium carbonate, magnesium carbonate, or combination thereof is acementitious material.
 9. The method of claim 8, wherein thecementitious material comprises vaterite.
 10. The method of claim 8,wherein the cementitious material has a compressive strength of greaterthan 10 MPa.
 11. A system comprising a Solvay system integrated with anelectrochemical system, comprising: a) a Solvay system comprising anabsorber configured to absorb carbon dioxide in an ammonia solution toform sodium bicarbonate; and b) a first electrochemical system operablyconnected to the Solvay system configured to convert the sodiumbicarbonate to sodium carbonate.
 12. The system of claim 11, furthercomprising a regenerator operably connected to the Solvay systemconfigured to regenerate the ammonia solution after absorption of thecarbon dioxide in the ammonia solution.
 13. The system of claim 12,further comprising a lime calciner operably connected to the regeneratorand configured to produce calcium oxide for regenerating the ammoniasolution.
 14. The system of claim 12, further comprising a secondelectrochemical system operably connected to the regenerator andconfigured to produce sodium hydroxide for regenerating the ammoniasolution.
 15. The system of claim 11, further comprising a precipitatoroperably connected to the first electrochemical system configured toproduce calcium and/or magnesium carbonate by treating sodium carbonatewith calcium and/or magnesium ions.